If I can remember to do it, I always "google" my witnesses and my adversary's witnesses before trial.
Usually there's not much interesting out there, or there's obviously too many people out there with the same name, but I'm always waiting for the day when I hit the jackpot and find a news story beginning with "[Prosecution's star witness] was convicted of perjury..." Never happens. (Well, it hasn't happened yet.)
But, I did find something that must be the next best thing... I found the prosecution's star witness on amiannoying.com. Seriously. And, get this, the overwhelming majority of the site's voters say that he is, in fact, annoying. Not an accurate scientific poll, of course, but let's just hope my jurors see it the same way.